The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.
The FAA has issued a reminder to pilots operating aircraft equipped with carburetors that gascolator problems are common and generally result in engine failure in flight.
Gascolator inspection during preflight can easily detect and prevent the most common gascolator problems.
The gascolator contains a fuel filter screen and a sediment bowl that serves as a water separator. Usually a gascolator has a wire bail holding a glass or metal bowl in place. There are three primary gascolator malfunctions, each of which can lead to a loss of power due to interruption in the fuel flow.
The gascolator bowl can separate entirely, which not only deprives the engine of fuel but also causes a fuel leak that can be a significant hazard during the ensuing forced landing.
The gascolator can leak because of improper gaskets or a loose bowl. The resulting fuel leak could cause a serious problem in flight. In addition, an engine-driven fuel pump can suck air into the system through the leak, making full power production impossible.
Finally, some gascolators feature quick-drain valves that allow the pilot to drain the bowl during preflight. Those valves occasionally develop leaks and have been known to separate in flight.
Checking the gascolator should be a standard part of the preflight inspection for all aircraft equipped with them. The bowl should be tight and the unit should show no signs of fuel leak.
Beech A-36 Bonanza
Engine Exhaust System Failure
While flying at 3,000 feet, the pilot noticed a sudden change of engine sound and smoke entered the cockpit. He landed safely at a nearby airport.This aircraft was equipped with a turbonormalized Continental engine installed under an STC. A technician examined the installation and determined the engine exhaust pipe was gone and there was severe heat damage in the engine compartment aft of the turbocharger. The brake lines and hoses were destroyed and a hole was burned in the left side of the engine pedestal mount.Part total time – 545 hours.
Beech 58TC Baron
During a scheduled inspection, the inspector noticed a loose rudder attachment.The technician disassembled the rudder and discovered two of the four fastener holes that attach the rudder mast to the bellcrank were elongated. All four bolts appeared to be tight.Part total time – 3,194 hours.
Beech A-90 King Air
The right engine failed while in cruise at 4,500 feet. All attempts to restart the engine failed, and the pilot made a safe single-engine landing.The technician discovered the high-pressure fuel pump did not supply sufficient pressure or volume to sustain engine operation. The fuel pump exhibited a sheared drive coupling spline. Part total time – 516 hours.
Beech B-100 King Air
Engine Accessory Defects
During a scheduled inspection, the technician discovered the left engine starter shaft was defective and worn far beyond serviceable limits.The technician also discovered the engine exhaust duct retention hardware was severely corroded. The exhaust duct retention hardware installed on the right engine was in the same corroded state and required replacement.This aircraft had received a double engine overhaul a short time prior to this inspection.Aircraft time since engine overhaul – 311 hours.
Cessna 172R Skyhawk
After returning from a flight, the pilot reported fuel was dripping from the lower fuselage surface.The leak was traced to a fuel system drain valve, but replacing the valve did not solve the problem. The mechanic found the leak source was a 2-inch long crack adjacent to a manufacturing weld on the lower leading edge of the fuel tank.
Cessna 172R Skyhawk
Suspect Induction Air Filter
During a scheduled inspection, the technician found the paper element of the induction air filter assembly badly eroded. Approximately 40 percent of the forward facing filter surface was eroded to a depth which penetrated the accordion folds of the filter. After removing the filter assembly, it was evident the filters filtering capacity was severely diminished.Cessna lists this filter for replacement after 500 hours time in service.Part total time – 300 hours.
Cessna U206B Super Skywagon
Nose Landing Gear Security
The nose wheel separated from the aircraft during landing.The technician searched the landing site and found the nosewheel attachment bolt and other hardware. When he found the nosewheel bolt, the nut was not attached but the bolt threads were not damaged. Along with the other hardware, he found a self-locking nut he could install on the bolt by using only hand pressure, apparently because it had been reused.
Cessna 550 Citation
Nose Landing Gear Security
While conducting an inspection, the technician found the nose landing gear trunnion loose.The screws used to secure the left and right nose gear trunnion supports were loose. There is no required inspection time for this assembly.The submitter found this defect on several other like aircraft with comparable operating time.Part total time – 4,783 hours.
Engine Fuel Starvation
Approximately 1 hour after takeoff, the left engine failed. The pilot turned on the auxiliary fuel pump, restarted the engine and landed safely.A technician discovered the engine-driven fuel pump that had recently been overhauled had failed internally, raising the possibility the pump was not overhauled properly.Part time since overhaul – 13 hours.
Piper PA-28-151 Warrior
Nose Gear Steering Defect
While conducting an annual inspection, the technician discovered a crack in the nose gear steering horn where it attaches to the nose gear strut. The crack may have been caused by excessive rudder pedal pressure with the aircraft stationary on the ground, a nosewheel-first landing or exceeding the turning limit while towing the aircraft. Part total time – 4,500 hours.
Piper PA-28-235 Charger
Defective Fuel System
During an annual inspection, the inspector discovered the main fuel sump screen almost completely obstructed.The technician found the reddish-brown material in the fuel screen came from the fuel tanks. It appeared a fuel tank sloshing compound was used inside the tank at one time and was disintegrating inside the tank. This aircraft was operated using auto fuel under an STC.
Piper PA-31-350 Chieftain
Hydraulic System Failure
The landing gear failed to extend normally, but the pilot used the emergency system and made a safe landing.A technician found the hydraulic system was leaking and the reservoir fluid level was very low. The source of the leak was a loose B-nut on the backside of the hydraulic system service port.
Piper PA-31-350 Chieftain
Wing Flap Failure
After landing the aircraft, the pilot retracted the wing flaps. The right flap retracted, but the left flap remained down.The technician found the left flap flexible drive shaft inoperative. The retaining washer failed and allowed the drive end of the shaft to retract inside the housing and disengage from the transmission. In addition, the split-flap protection system did not function because the time-delay relay had failed.Part total time – 210 hours.
Piper PA-32R-300 Lance
Stabilator Trim Control Damage
The pilot reported the manual stabilator trim adjustment was inoperative during flight.The plastic trim control wheel was severely worn in the area of the detent receptacle, which engages the swaged ball on the control cable. The damage may have resulted from attempts to override the electric trim system.Part total time – 2,441 hours.
Engine Power Failure
During flight, the pilot lost engine power and landed the aircraft on a grass airstrip. A maintenance technician discovered the engine failure was caused by fuel starvation. The inner lining of the fuel hose running from the sump to the carburetor was loose and swollen, severely restricting the fuel supply to the engine. The fuel hose was constructed of Specification MIL-H-6000 hose stock and was manufactured in 1985.The defect could have been a function of age or that the fuel line had been exposed to auto fuel used in the aircraft for several years in accordance with an STC.Part total time – 15 years.